Tell us about yourself!
What's ATF? I looked it up and got "Federal Bureau of Alcohol, Tobacco, and Firearms." That ain't it, right?
OK: Automatic transmission fluid.
I remember that from my tour to the Colosseum in Rome: Only male urine because there were no restrooms for women there(!), and only from the upper class patrons, who had separate public toilets with troughs where the urine was collected. They thought that richer men would be eating better, and thus, has "better" urine. I can't imagine that they didn't regularly have plenty bacteria in their mix!
Nice idea! For sizing, remember: Because of their dislocatable "shoulders," rodents can squeeze through teeny holes. Mice can fit through a hole the size of a dime. Rats can fit through a hole the size of a quarter.
$10 Smartphone to digital microscope conversion!